import <Utilities/Conversion.sl>;

main(args(2)) :=
    run(args[1], stringToInt(args[2])) when size(args) = 2
else
    "Usage error: exec <initialCells> <generations>";

stringToCells(string(1))[i] := 0 when string[i] = '_' else 1;
cellsToString(cells(1))[i] := '#' when cells[i] = 1 else '_';

run(cellsString(1), generations) :=
        runHelper(stringToCells(cellsString), generations, cellsString);

runHelper(cells(1), generations, result(1)) :=
    let
        nextCells := step(cells);
    in
        result when generations = 0
    else
        runHelper(nextCells, generations - 1,
                  result ++ "\n" ++ cellsToString(nextCells));

step(cells(1))[i] :=
    let
        left := cells[i-1] when i > 1 else 0;
        right := cells[i + 1] when i < size(cells) else 0;
    in
        1 when (left + cells[i] + right) = 2
    else
        0;